th This book contains most of the papers presented at the Iy Inter- national Symposium on Bone Circulation which was held in Tou- louse, France, in September of1987. The symposium was attended by over 200 specialists from 17 different countries. Some of them were in Toulouse for the fourth time to discuss their favourite topic of study and research: bone circulation, its exploration, its pathol- ogy. Many, including a group of Japanese orthopaedic surgeons, were present for the first time, delighted to meet the authors of papers they had read. There were more than 100 oral presentations and posters, but many meaningful informal discussions took place both in and outside of the auditorium, in the hall and during meals. The organizers wished to maintain a balance between funda- mental themes and subjects of clinical and practical interest. This balance was accomplished: recent developments including scintig- raphy, magnetic resonance imaging and bone grafts played just as important a part as more sophisticated topics such as the evalua- tion of the blood flow rate in animal bone tissue. Thus, as did the previous symposia, this book aims to present a progress report on developments during the last 5 years in the study of bone circulation. We wish to thank all those who helped and encouraged us throughout the organization of the congress, especially C. Ar- noldi, M. Brookes, R. Burkhardt, L. Coutelier, S.P.F. Hughes, P. Kehr, J.P. Jones, A. Trias, K.Ono, T. Yizkelety and G.J.